It’s hard not to notice that the range of gluten-free foods available in supermarkets has increased massively in recent years. This is partly because the rise in the number of people diagnosed with coeliac disease and gluten sensitivity, and partly because celebrities, such as Gwyneth Paltrow, Miley Cyrus and Victoria Beckham, have praised gluten-free diets. What used to be prescription-only food is now a global health fad. But for how much longer? New research from Harvard University has found a link between gluten-free diets and an increased risk of developing type 2 diabetes.

Gluten is a protein found in cereals such as wheat, rye and barley. It is particularly useful in food production. For example, it gives elasticity to dough, helping it to rise and keep its shape, and providing a chewy texture. Many types of foods may contain gluten, including less obvious ones such as salad dressing, soup and beer.

The same protein that is so useful in food production is a nightmare for people with coeliac disease. Coeliac disease is an autoimmune disorder in which the body mistakenly reacts to gluten as if it were a threat to the body. The condition is quite common, affecting one in 100 people, but only a quarter of those who have the disease have been diagnosed.

There is evidence that the popularity of gluten-free diets has surged, even though the incidence of coeliac disease has remained stable. This is potentially due to increasing numbers of people with non-coeliac gluten sensitivity. In these cases, people exhibit some of the symptoms of coelaic disease but without having an immune response. In either case, avoiding gluten in foods is the only reliable way to control symptoms, that may include diarrhoea, abdominal pain and bloating.

Without any evidence for beneficial effects, many people without coeliac disease or gluten sensitivity are now turning to gluten-free diets as a “healthy” alternative to a normal diet. Supermarkets have reacted to meet this need by stocking ever growing “free from” ranges. The findings of this recent study, however, suggest that there could be a significant drawback to adopting a gluten-free diet that was not previously known.

Inverse association

What the Harvard group behind this study have reported is that there is an inverse association between gluten intake and type 2 diabetes risk. This means that the less gluten found in a diet, the higher the risk of developing type 2 diabetes.

The data for this exciting finding comes from three separate, large studies that collectively included almost 200,000 people. Of those 200,000 people, 15,947 cases of type 2 diabetes were confirmed during the follow-up period. Analysis showed that those who had the highest intake of gluten had an 80 percent lower chance of developing type 2 diabetes compared to those who had the lowest levels of gluten intake.

This study has important implications for those who either have to avoid or choose to avoid gluten in their diet. Type 2 diabetes is a serious condition that affects more than 400m people worldwide—a number which is certain to increase for many years to come.

Collectively, diabetes is responsible for around 10 percent of the entire NHS budget and drugs to treat diabetes alone cost almost £1 billion annually. There is no cure for type 2 diabetes and remission is extremely rare. This means that once diagnosed with type 2 diabetes, it is almost impossible to revert back to being healthy.

It is important to note that the data for this study was retrospectively gathered. This allows for very large numbers to be included but relies on food-frequency questionnaires collected every two to four years and the honesty of those recruited to the study. This type of study design is rarely as good as a prospective study where you follow groups of people randomly assigned to either have low- or high-gluten diets over many years. However, prospective studies are expensive to run and it’s difficult to find enough people willing to take part in them.

While there is some evidence for a link between coeliac disease and type 1 diabetes, this is the first study to show a link between gluten consumption and the risk of type 2 diabetes. This is an important finding. For those who choose a gluten-free diet because they believe it to be healthy, it may be time to reconsider your food choices.